Much work has been directed to dispensing packages for liquids and other fluent masses. Swedish Pat. No. 197,618, which issued to K. H. Lundberg on Jan. 21, 1965, from an application filed June 21, 1961, for example, discloses a receptacle for paste-like or liquid material comprising a transparent tube equipped on one end with a tapering flexible hollow head having a slit opening therethrough. In one version of the receptacle described by Lundberg, the transparent tube is equipped with a plunger provided with a number of ring-shaped flanges extending obliquely from the plunger in a backward direction relative to the hollow head. The ring-shaped flanges extending in a backward direction permit the plunger to be easily moveable toward the hollow head, but moveable in the opposite direction only " . . . by overcoming the significantly increased friction." In use, a portion of the hollow head is manually squeezed together thereby reducing the volume within the head and discharging material through the slit. Upon release of the squeezing force, the slit closes as the hollow head returns to its original volume, thus creating a slight underpressure within the receptacle and thereby moving the plunger in a direction toward the hollow head.
A container adapted to hold semi-solid or fluent masses and embodying dispensing features for controlling the discharge of such masses is disclosed in U.S. Pat. No. 3,088,636, which issued to Walter B. Spatz on May 7, 1963. The Spatz '636 dispenser describes a container having a pliant plastic head capable of decreasing the effective volume within the container, a self-closing discharge opening which acts as a check valve, and a one-way follower device. Inward deflection of the pliant head decreased the volume within the dispenser and effects an opening of the discharge outlet, thus allowing the fluent material to pass therethrough. A one-way latch mechanism is attached to the central rear portion of the follower and includes a plurality of circumferentially spaced latch fingers which extend laterally in an outward and rearward direction and function to engage the inner wall of the container to prevent rearward motion of the follower device within the container. Upon release of the pressure on the head, the lips of the discharge outlet are closed and the head resiliently returns to its original configuration, thus creating a partial vacuum within the container and allowing atmospheric pressure to act on the one-way follower device pressing it forwardly within the container.
U.S. Pat. No. 3,768,705, which issued to Walter B. Spatz on Oct. 30, 1973, is also directed to a dispenser for fluent masses and shows a one-way follower slidingly mounted within a pliant elastic container behind the fluent material contained therein. A butterfly check-valve is disposed in the outlet of the elastic container and opens to allow dispensing in response to squeezing of the container at any point. Subsequent to the removal of a squeezing force on the elastic container, the outlet check-valve closes, thus preventing air from entering the container as the pliant container walls return to their original position, thereby creating a negative pressure within the container. The follower comprises a one-way latch device similar to that described in the Spatz '636 patent having rearwardly disposed latch fingers which prevent movement of the follower in the rearward direction. As in Spatz '636 ambient air at atmospheric pressure moves the follower forwardly within the container as the result of the vacuum created after a dispensing operation.
A pump-action dispensing package for liquids and paste-like products is taught in U.S. Pat. No. 4,301,948, which issued to Joachim Czech and Hans Sieghart on Nov. 24, 1981. This dispenser features a container closed at its lower end by a slidable piston and provided at its upper end with a head member which includes a variable-volume pump chamber. The pump chamber itself is isolated from the bulk of the product in the container by a first check valve adapted to open only towards the pump chamber, and is isolated from an extended outlet passage by a second check valve adapted to open only towards the outlet. Exterior manual pressure exerted on the pump head piston decreases the volume in the pump chamber and forces product through the second check valve and outlet, thereby dispensing a portion of the product. Upon removal of said force, the pump chamber returns to its original volume thereby creating a partial vacuum within the pump chamber and causing the second check valve to close and the first check valve to open, thus permitting product from the container to enter the pump chamber and replace the mass of product which had been dispensed.
Despite all of the prior work done in this area, as evidenced by the above-cited patents, there remain problems of complexity of the dispensers, assembly of the parts, reliability of function, and excessive cost. The packages of the prior art require complex multiple valving structures, and/or multi-part follower devices, and/or correspondingly complex assembly operations, and still are not always reliable in operation. Further, heretofore pump dispensers have required either a one-way follower device or a set of at least two check valves to operate properly. Such shortcomings result in dispensers which are necessarily complex, inconvenient, and expensive.